1. Field of the Invention
This invention relates to a drawbar assembly for connecting together railroad cars, in general, and, more particularly, to a drawbar arrangement embodying a simplified construction and arrangement of parts that includes a drawbar with a truncated convex spherical end contained between a front draft bearing surface formed integrally with a drawbar support housing which is secured to a center sill and a rear support block which is supported against the housing by a gravity-activated wedge.
2. Description of the Prior Art
As is known, most prior art railroad coupler assemblies are relatively complicated and include a draft sill, draft gear, yoke, follower block, striker, pin or coupler connection and the coupler itself and its associated components. Such conventional coupler arrangements have a degree of free and cushioned slack. That is, there is a certain amount of free "play" between the coupler components when the load changes from a draft to a buff load, and vice versa. At the same time, the draft gear acts as a spring mechanism to cushion impacts between adjacent cars. Research has indicated that eliminating the free and cushioned slack within a train can eliminate over the road train action forces due to "run-ins" and "run-outs". The magnitudes of these forces are large and cause significant wear and tear on the rolling stock and in some instances are severe enough to cause derailments.
Furthermore, in conventional coupler assemblies, the key or pin connection of the coupler to the yoke is at a relatively long distance from the kingpin about which the wheel truck rotates. In negotiating curves, particularly under buff loading conditions, this gives rise to relatively large lateral forces which can cause derailments. The same is true when jackknifing occurs under buff loads with lateral forces attempting to rotate the cars about their centers.
An improvement to the aforesaid conventional coupler assemblies was disclosed in U.S. Pat. No. 4,580,686, the disclosure of which is incorporated herein by reference. While not limited thereto, that patent, as well as the present invention, was particularly adapted for use in unit train applications where cars are coupled and uncoupled for periodic maintenance and repair only. Such cars are not subjected daily to impact forces associated with bumping encountered in classification yards and, therefore, do not require cushioning devices such as draft gears.
Specifically, that patent provided a drawbar arrangement for coupling railroad cars each having a center sill and trucks at its opposite ends, the trucks being pivotal about vertical kingpins. The arrangement included a drawbar having an enlarged spherical butt end portion defining essentially convex spherical buff and draft load surface, a rear support block having a tapered rear surface and concave substantially hemispherical buff load bearing surface adapted to engage with the convex buff load bearing surface of the butt portion, a slack adjusting wedge for engaging the tapered surface of the rear support block, means for transferring buff loads from the slack adjusting wedge to the center sill, a front draft block having a concave and substantially hemispherical draft load surface adapted to engage with the convex draft load surface of the enlarged spherical butt end portion, the front draft block including an annular draft load surface opposite the hemispherical draft load surface thereof, a wear block having an annular draft load surface adapted to engage the annular draft load surface of the front draft block, and means supported by the center sill for transferring a draft load from the wear block to the center sill.
Preferably, the drawbar arrangement of U.S. Pat. No. 4,580,686 provided that the draft block and the wear block each have an opening wherein the shank of the drawbar extended in a direction which was generally opposite the kingpin. The aforesaid means supported by the center sill included a plurality of draft stop lugs supported by the center sill. A sill bottom plate was preferably secured to the center sill for supporting one of the plurality of draft stop lugs. The center sill included spaced-apart sill side walls extending along opposite sides of a sill roof wall. The drawbar arrangement preferably further included a carrier plate supported by the center sill opposite the roof wall thereof for supporting the rear support block, front draft block and the wear block between the side walls of the center sill. The tapered surface of the slack adjusting wedge was preferably arranged to extend in a vertical direction along the height of the side walls of the outer sill. The tapered thickness of the wedge was greater at the top thereof than at the bottom for movement under the force of gravity between the rear support block and the lugs supporting the wedge on the center sill. An opening in the front draft block was preferably longer in the vertical direction than in the horizontal direction, whereby the draft front block rotated with the drawbar shank portion in a horizontal plane but not in a vertical plane. Moreover, the rear support block and front draft block rotated in an endless manner about an axis extending substantially along a central longitudinal axis of the shank relative to the convex spherical buff and draft load surfaces. The pivotal action at the end connections facilitated rotation, and permitted 360.degree. rotation for negation of horizontal and vertical track curves as well as rotary car dumping.
With an arrangement of that sort, free and cushioned slack was eliminated form the interconnection between cars, thus eliminating undesirable longitudinal train action forces and reducing the risk of derailment. The slackless connection between cars provided thereby eliminated run-in and run-out of slack between cars in reversals of draft and buff train actions. That also eliminated the generation of large forces due to relative accelerations between cars, thus reducing wear and damage to car components, lading and locomotives, thereby reducing maintenance cost. The design of the drawbar reduced an estimated 650 pounds from the tare weight of the car and eliminated couplers, yokes, cushioning devices and strikers. At the same time, the structure forming the pivotal connection at each end of the drawbar could be incorporated into existing center sills without modification of the center sills. Moreover, the site at which the structure used to interconnect the end of the drawbar with the center sill could be located at any desired location but preferably rearwardly of the car to reduce lateral wheel force components. By moving the pivot point of the drawbar toward the center line of the bolster, car tracking through tight radius curves was enhanced while reducing the potential for track overturn plus wheel wear. That invention further utilized a gravity-activated wedge which was arranged to move vertically to compensate for wear and maintain a slackless relationship of parts that interconnected the drawbar with the car.
While the structure disclosed in U.S. Pat. No. 4,580,686 represented an improvement over prior conventional coupler assemblies, it required rather difficult assembly and disassembly and was subject to significant wear caused by friction.
For example, if either the front load bearing block or the wear block needed repair or replacement, a weld or other connecting means joining oppositely-directed shanks which formed the drawbar had to first be destroyed or otherwise removed to release the shanks from one another. The drawbar could then be removed from the center sill by removing the sill bottom cover plate which held the front and rear load bearing blocks about the enlarged spherical end portion of the drawbar. Once the drawbar was removed from the sill, the front block and/or the wear block were then slidably removed from the shank. Then, a repaired or a replacement front block and/or wear block was slid back onto the shank of the drawbar. Upon completion of the maintenance, the drawbar assembly was reassembled and the oppositely-directed shanks were then rewelded or otherwise connected to form a continuous drawbar.
Also, the large area of surface contact between the spherical butt end portion of the drawbar and mating spherical portions of the front draft block and rear buff block led to the creation of significant friction between and, consequently, premature wearing and failure of those contacting parts.
An advantage exists, therefore, for a slackless rotary drawbar assembly which is easily assembled and disassembled and which has a high degree of reliability.
It is therefore an object of the present invention to provide a slackless rotary drawbar assembly which is easily assembled and disassembled.
It is a further object of the present invention to provide a slackless rotary drawbar assembly having a reduced likelihood of premature wear and failure of its constituent parts.
Still other objects and advantages will become apparent in light of the attached drawings and written description of the invention presented herebelow.